In the past, methods for the fixation of fractured long hollow bones involved the use of a bone plate with screw holes to which all the pieces of a fractured bone were secured. However, such procedures required large operative openings which increased the risk of infection. Further, it was necessary to remove the metal bone plates after several years, since the holes through which the bone nails passed weakened the bone and caused the bone plate to absorb stress on the leg.
The shortcomings of using bone plates led to the development of a semi-invasive method for external fixation of pins through the skin to connect bone to an intramedullary rod. This procedure required a 2-inch incision through which a guidewire was passed for insertion of an open, channeled, intramedullary rod to which the pieces of bone were connected. While this approach reduced operating time and placed the pieces of bone in better alignment, it was eventually discovered that this method did not prevent the intramedullary rod from rotating during walking and other movement of the leg.
U.S. Pat. No. 4,519,100 to Wills et al. attempted to overcome the problems caused by rotation of an intramedullary rod by using a plurality of pivotable blades which rotate outwardly to engage the distal end of a fractured bone. In this method, the blades are pivotably coupled to a connector member, which translates longitudinally in either direction within an elongated shaft. Translation of the connector member towards the front end of a covering sheath resulted in the outward rotation of the blades into the bone at its distal end. With the device inserted lengthwise into the bone, the bone-engaging mechanism was supposed to prevent rotation, angulation, and antero-posterior translation. However, a longitudinal track defined along the entire length of the covering sheath has been found to cause loss of torsional rigidity. In addition, problems have been encountered with deployment of the engagement fins.
One method which seeks to overcome these problems is the Russell-Taylor interlocking nail system, in which screws are placed at both ends of an open channeled, cloverleaf-shaped Kirchner rod. It has been found that when this type of rod is put in a circular medullary canal, compression results on three points of the rod, causing the bone to resorb and allowing the rod to rotate.
According to the Russell-Taylor interlocking nail system, an oblique skin incision is made 2 cm distal to the proximal tip of the greater trochanter and continued proximally and medially for 8-10 centimeters. The fascia of the gluteous maximus is incised in line with the skin incision.
A curved awl, designed to enlarge the entry portal, is introduced at the trochantric fossa in line with the femoral shaft. The blunt tip of a tapered T-handle reamer is used to enlarge the metaphyseal canal.
A ball-tip guide rod is introduced into the bone to the level of the fracture. Containment of the guide rod within the femur is confirmed by antero-posterior and lateral image intensification. After reaming of the proxima femur, an alignment device is inserted.
A guide pin is extended into the distal fragment until the tip reaches the old epiphyseal scar or distal pole of the patella, after which the alignment device is removed. Containment of the guide rod within the femur is verified by image intensification. A C-arm is used to determine a proper length with a nail length gauge.
A medullary alignment tube is introduced over the guide rod to maintain fracture reduction. The ball-tip guide rod is replaced with a nail guide rod, and then the medullary alignment tube is removed.
A locking nail is entered into the distal fragment by several centimeters through a proximal drill guide. The nail is then driven so that the proximal end is flush with the tip of the greater trochanter. For distal attachment, a distal incision is made immediately before the distal "targeting" procedure. An image intensifier is used to assist in locating the nail holes in the locking nail. The holes should appear as perfect circles for proper alignment of distal bone fragment nails.
The use of a fluoroscope or image intensifier used in this and other procedures is made to assure alignment of the screws with the inserted rods (targeting). A surgeon views the intended area of placement of a screw and places his or her hands in the field of view to position a screw with respect to a drilled hole. This method has raised the concern of repeated exposure to small doses of radiation, which may be cumulative in affecting a surgeon's health over time.
Another method of use of a femoral nail system is described in a brochure entitled "AO/ASIF Universal Nail," by Synthes.
In U.S. Pat. No. 4,622,959 to Marcus, an intramedullary nail is described for use in repairing fractures of the left or right femur. The nail includes a body having a head, an intermediate portion, and a distal tip. Transverse openings are provided in the body near the distal tip and in the head for receiving locking screws. One opening in the head has its axis within the femoral neck, and another opening has its axis generally transverse thereto. The proximal nail head has a seat with a transverse locating slot for securing a screw insertion tool in a fixed angular position. A screw guide on the tool is aligned with one of the screw-receiving openings.
By the method and apparatus of the present invention, the problems encountered with the previously known procedures have been overcome.